There are a total of 4000 primes. Collect 2000 public keys and some of them should share the same prime.

Collection code: [https://github.com/CTF-STeam/ctf-writeups/blob/master/2020/COMPFEST/mutual-friend/get_data.sh](https://github.com/CTF-STeam/ctf-writeups/blob/master/2020/COMPFEST/mutual-friend/get_data.sh)

Solver code: [https://github.com/CTF-STeam/ctf-writeups/blob/master/2020/COMPFEST/mutual-friend/solve.py](https://github.com/CTF-STeam/ctf-writeups/blob/master/2020/COMPFEST/mutual-friend/solve.py)

Flag: `COMPFEST12{Euclid_W0ulD_b_Pr0Ud_Ov_4l1_7h3sE_MetH_eXpeRt5_a39e7a}`

Original writeup (https://github.com/CTF-STeam/ctf-writeups/tree/master/2020/COMPFEST/mutual-friend).